In an electrostatic precipitator for the recovery of solid particles from a gas stream, it is conventional to configure the collector electrodes as a plurality of generally parallel and preferably upright conductive curtains, which define therebetween generally flat channels or flow paths for the gas stream. Corona-discharge electrodes in the form of wires or the like, may be provided in arrays between the curtains and a dust or particle collecting bin is formed below the curtains. The curtains shed the accumulated dust and solid particles when vibrated by a rapper which provides impact at a rigid member of a structure attached to the electrodes.
In all such electrostatic precipitators, it is important to maintain the planarity of the collector curtains since any distortion may dispose a portion of a collector more closely than is desired and may result in an electrical breakdown across the space between curtain and discharge electrode. Of course to simply avoid the danger that the gap will close to an extent that such breakdown will occur by originally spacing the electrodes apart to a considerable extent, creates the disadvantage that the apparatus becomes less efficient and requires more space for a given volume of gas processed, solids recovered, etc.
Curtains warp due to age and expansion and/or temperature, whereby the efficiency of the electrostatic precipitator is greatly reduced. As the spacing between adjacent electrodes and curtains decreases, the degree of flash discharging therebetween increases and the effectiveness of the precipitator curtains to remove dust and/or soot decreases. The prior art has suggested that spacers be disposed between adjacent electrodes or curtains to prevent the distance therebetween from decreasing.
In the prior art, U.S. Pat. No. 4,007,023 of Batza et al. discloses parallel disposed precipitator electrodes or curtains between which is disposed a plurality of spacers. Spacers are mounted on one curtain and extend toward the other in substantially perpendicular relation thereto. The spacer is dimensioned slightly less than the normal spacing between adjacent curtains so as to provide an air gap between its distal end and the other curtain. A spacer is adapted to pivot up and away from the other precipitator curtain. Batza et al. discloses spacers that are not adapted to be installed upon an existing precipitator curtain and are relatively permanently fixed to the curtains.
In a further solution of the prior art as described in an article entitled "Restore Megawatts Lost to Compliance Deratings", POWER, 5/84, spacers in the form of U-shaped members are disposed between adjacent curtains of an electrostatic precipitator. Typically, curtains are conventionally constructed to have evenly spaced and vertically disposed stiffeners or ridges disposed vertically along their length. Such U-shaped members and, in particular, the leg portions of the U-shaped members are disposed in a vertical orientation and are welded to opposing stiffeners of adjacent curtains. Typically, a number of such U-shaped spacers is welded along the vertical extent of adjacent curtains. In order to install such U-shaped members, it is necessary to shut down the operation of the electrostatic precipitator to permit skilled technicians to secure, typically by welding, the spacers between the adjacent curtains.
A further solution takes the form of a ladder-like arrangement comprised of a plurality of sections that are connectable end-on-end to each other. Each section resembles a parallelogram and is comprised of two upright members of substantially equal length, disposed parallel to each other and separated by a pair of pivotally mounted legs, likewise disposed parallel to each other. The legs are pivoted so that the upright members may be disposed adjacent to each other in a collapsed condition, thus permitting the insertion of one section between adjacent curtains. One section may be connected, typically by rivoting, to another to form the spacer arrangement of a length coinciding to the length of the adjacent curtains; the top of one section is connected to the bottom of the next higher section. The topmost section has a pair of hooks which are connected to the upright members and serve to suspend the ladder-like arrangement to the curtain support bars. After insertion, the upright members are separated until the legs are substantially horizontal, whereby the ladder-like arrangement provides a maximum and substantial even spacing between adjacent curtains. Such an arrangement suffers the disadvantage of relatively high weight and expense of construction. Typically, curtains employed in precipitators may extend vertically some 35 ft. in length. A typical section is 3 ft. in length and weighs in the order of 10 lb. Thus, 8 or 9 sections weighing in excess of 75 lbs. must be assembled and lowered between adjacent curtains. Often the personnel assembling and mounting such spacers work in cramped spaces and experience has shown that it is most difficult to lower an assembly of such weight into place between adjacent curtains, while avoiding interference with the corona-discharge electrodes. Once in place, the upright members of such a ladder-like arrangement may be most difficult to separate, especially if there is a number of warpage points along the length of the adjacent curtains. Due to the collapsible nature of such a ladderlike arrangement, care must be taken not to allow one's hands to be caught between the upright members and the legs.